A multilayer electrolytic capacitor is used around a CPU of a notebook computer. This electrolytic capacitor is needed to have characteristics such as large capacity, a low ESR (Equivalent Series Resistance), a low ESL (Equivalent Series Inductance), and high reliability. Since a power supply has used a higher frequency in recent years, the ESL characteristic among others needs to be improved. The electrolytic capacitor encountering these demands from the market is described hereinafter with reference to FIG. 10 and FIG. 11, which are sectional views of a conventional electrolytic capacitor.
Conventional electrolytic capacitor 1 includes multilayered sheets of capacitor elements 4, a pair of positive electrode terminals 5, negative electrode terminal 6, and outer-package resin 7. Each of capacitor elements 4 includes positive electrode 2 at one end and negative electrode 3 at another end. Positive electrode 2 is connected to a top face of positive electrode terminal 5, and negative electrode 3 is connected to a top face of negative electrode terminal 6. Outer-package resin 7 covers capacitor elements 4 such that at least parts of undersides of positive electrode terminal 5 and negative electrode terminal 6 are exposed outside.
As FIG. 10 shows, each of positive electrodes 2 of capacitor elements 4 is oriented in opposite directions to each other alternately, and negative electrode terminals 6 are disposed between the pair of positive electrode terminals 5. This structure allows the magnetic fields to weaken each other, thereby lowering the ESL. Positive electrodes 2 of capacitor elements 4 and positive electrode terminal 5 are connected together by laser welding. This connection allows lowering the ESR and the ESL of electrolytic capacitor 1.
As FIG. 11 shows, both the ends of positive electrode terminal 5 are bent to form upper stage 8, and positive electrodes 2 are disposed on a top face of upper stage 8 or lead-frame 2A incorporating positive electrodes 2 is disposed on a top face of upper stage 8. Positive electrodes 2 are welded to upper stage 8 or lead-frame 2A is welded to upper stage 8. Although a scar from the welding (a welded mark) is left on a rear face of upper stage 8, it can be embedded in outer-package resin 7, so that only a flat region can be used as a mounting face. This structure allows improving a mounting reliability as well as a bonding reliability between positive electrode terminal 5 and outer-package resin 7 (e.g. refer to Patent Literature 1).